We have a web application that uses AJAX to talk to an ASP.NET web service. We would like to write another version that can be used offline. We need to be able to re-use our existing code as much as possible. What approaches should we consider?
The app is currently using XmlHttpRequest to get dynamic data from the server. Obviously the offline version will not be able to talk to the server, but it does need to talk to something! I'm sure installing IIS or Cassini on the client would work, but I was hoping for a simpler solution. Is there no other way for JavaScript to talk to some external code?
There are plenty offline web apps nowaday. It simply evolve from AJAX.
For example:
WoaS (wiki on a stick / stickwiki), Tiddly Wiki,
Google doc and Gmail is going to be offline.
You don't need a webserver to run these webapps in offline mode. Just store the required data, scripts on the client side (usually as XML).
One of the possibilities would be to use Cassini. This is a web server that acts as a host for the ASP.Net runtime. You can host Cassini in a Windows application or a Windows Service. In this scenario you do not have to rewrite the web app and the web service.
Most other solutions do require a rewrite of both your web app and your web service. Depending on the way you have written the existing app you can reuse more or less code.
Have you considered HTML5 with application cache and offline storage?
If you hope to create an "offline" version of your package your biggest issue by far will be the need to install your site into a local copy of IIS (registering a virtual directory, etc.). I pursued this briefly a few years ago and gave up in frustration. It can be done: a number of software vendors such as DevExpress do this so you have local copies of their demonstration projects. Indeed, I was able to do this. The problem was the classic "it works on my computer" syndrome. There was simply no way to guarantee that most of my end-users had anywhere near the technical proficiency to make this work.
Thus, I would strongly recommend that you not pursue this path unless you have very technically proficient users and a huge support staff.
But there is one more very important question: did you abstract all data access code to a DAL? If not, then you have a lot of work to do in managing data access as well.
Update: user "Rine" has recommended Cassini. I just wanted to let you know that I pursued Cassini and another 3rd-party web server as well. I think that there are licensing issues with Cassini but may be wrong - it has been awhile. However, I do distinctly remember running into barrier after barrier with this approach and very little documentation to help me out.
if you want a web application run offline, you need a webserver (IIS for ASP) bound to the localhost (127.0.0.1) address. After this so can access your web application by typing http://127.0.0.1/ in your web browser the same way as you do online.
If your AJAX relies on XMLHttpRequest's, you can:
Make the static versions of XML's you get over XMLHttpRequest and put then into a folder on disk.
Rewrite your XMLHttpRequest URL's so that they point to files on disk.
Rewrite your XMLHttpRequest's so that they don't check status (it's always 0 for the file:// protocol.
All JScript works on file:// pages as well as on http:// ones.
Of course it's not the best way to develop static pages, but it may save you some time on rewriting.
I havent come across any framework specifically built for asp.net like the ones available for PHP or RoR.
Here is a good article by Steven to get you started with HTML 5 and ASP.Net Creating HTML 5 Offline application
Obviously the offline version will not be able to talk to the server, but it does need to talk to something!
Enter HTML5 LocalStorage. It works like a database and enables you to put data on your client. Indeed you have to rework parts of your code in javascript and transmit it to the client, but then it would work offline.
Local Storage works like this:
- Setter: window.localStorage.setItem(KEY, VALUE)
- Getter: window.localStorage.getItem(KEY)
- Remove: window.localStorage.removeItem(KEY)
To get the main page working offline you need to create a manifest. This is used to store complete sites on the client. Please refer to this for more information about manifests:
http://diveintohtml5.info/offline.html
You want to build a web application to work offline?? It can't be done.
You could split the interface code from the rest (in diferent dlls) and create a windows application to mimic the behaviour of your web application. This way you have 2 distinct user interfaces but the same code for business rules and data access.
I don't really see any other way...
Related
I'm using Python and QT (PySide) in a local application (which connect to a database on cloud Azure).
Now, my objective is moving this app on the web, in particular on Azure (I have an Azure subscription), simply transfering it on Azure, it's possible in some manner? I have not found examples on the web.
The important question is: is Python QT (app web) compatible with Azure?
Thanks
UPDATED ANSWER!
Yes, now you can. Well sort of. The mad mads at Digia have created something called "QT for Web Assembly" that can compile your whole app into something that runs embedded into a web page.
https://doc.qt.io/qtcreator/creator-setup-webassembly.html
You might have to rethink connecting directly to the database however, as thats simply not gonna fly with web-sockets (And honestly direct app to remote RDBMS has never been a smart move. Theres a LOT of things that can go wrong letting the internet connnect to your databaes). But you could at least keep the UI and rewrite the databaes layer to interogate something like a GraphQL (or whatever) front end to the data.
OLD ANSWER
I'm afraid your up for a nearly complete rewrite. QT is a desktop/mobile platform. It doesn't go anywhere near HTML/CSS except perhaps for displaying them in a webview component. Azure or AWS won't magically make it into a web application for you.
Your code as it stands needd to be rewritten in a web-first transactional manner. That is it takes a request, processes it, produces a result. To some extent websockets has changed this dynamic for a limited subset of use cases where interaction needs to be non transactional, and modern web app design hides much of the transactionality behind a web-services model, but 90% of web work is still very much transactional.
Database <---> Web server/Web app stack <--- Internet! --> Web browser
My suggestion is to pick up Django (or one of the other systems. If its just simple, Flask is another good alternative. Flask for simple apps, Django for the big stuff. Or use something else, you have choices here!, and start from scratch. Analyse your products function and start mapping out how to make this work as a database driven transactional system.
Theres no shortcuts here, I'm afraid.
Dear developer friends,
I have developed a self-hosted API in ASP.Net MVC4 (e.g. http://blogs.msdn.com/b/henrikn/archive/2012/03/01/file-upload-and-asp-net-web-api.aspx), because I needed a solution where I could upload super large files. This works smoothly.
Now I want to upload files to my newly written API through the Bluimp JQuery Upload component.
This works fine, except for some small flaws:
- the progress-bar is not showing
- JQuery raises an error: Unsafe JavaScript attempt to access frame with URL...
It seems clear that this error is raised, because my API runs on another port than the web application, and ajax calls cannot be made over cross domains / ports.
I have already added the forceIframeTransport: true parameter to the fileupload component call. This does some good - without it I cannot upload files at all (because the component tries to upload with an ajax call).
So.. I figured that if there's some way to run my self hosted API on the same port as my web-application (with explicitly defined routes), my world will be happy and shiny again. However.. I'm not quite sure whether this is possible at all..
Unfortunately a proxy from my ASP.Net application will not help me here, as I wrote the API to avoid the IIS limitations (regarding maximum upload size). Using my self hosted API as proxy might to the job, but I think this is a bit.. overkill?
Anyone? Thanks in advance!
Yahoo! Solved it!
var config = new HttpSelfHostConfiguration("http://localhost:49302/api");
In other words - the web api ONLY works when the url starts with /api. All other requests are picked up by my MVC4 web application. But they run on the same port.
So to answer my question: yes it's possible. Just add a root directory.
I came across a case study few days early. It is related to a web application architecture.
Here is the scenario,
There is a single web service used by say 1000 web applications. This web service is hosted on a particular server. If web service hosting location is changed, how the other applications come to know about this change ?
Keeping it in web.config doesn't seems to be a feasible solution as we need to modify web.config files for all the applications.
Keeping these settings in a common repository and let all the applications use it for web-service address was came in my mind, but again there is a question of storing this common repository.
I am just curious to know about how this could be achieved with better performance.
Thanks in advance for any kind of suggestions.
do you have full access or control over all those web applications consuming that web service? if so, you could have a script or some custom code which updates all their web.config(s) at once. it seems too much work but in fact in this way you have more control and you could also, eventually, point to the new url only some applications and leave some others on another url.
the idea with the setting in a centralized database gives you faster update propagation which could also be bad in case of errors and then you have all applications referring to the same place and no way to split this. Then you have anyway to connect to a centralized database from all of them and maybe you should add a key to their web.config(s) with the connection string to that database, then, in case that database is not reachable or is down, the web applications will not be able to consume the web service simply because they cannot get the url of it.
I would go for the web config, eventually you could have a settings helper class that abstract the retrieval of that url so the UI or front end does not know from where that url comes from.
anyway, do you plan to change the url of a web service often? wouldn't be better to copy it to a new url but to also keep it available on the current url for a while?
another advantage of web.config approach is that everytime you update and save it the application is restarted while a change in a database might take a while to be detected in case you have some caching mechanism,
hope this helps.
Davide.
I realise that this is going to be a fairly niche requirement and will almost certainly raise a few "WTF's" but here goes...
Within an ASP.NET Webforms application I need to serve static content from a local client machine in order to reduce up-front bandwidth requirements as much as possible (Security policy has disabled all Browser caching). The idea is to serve CSS, images and JavaScript files from a location on the local file system referenced by filesystem links from within the Web application (Yes, I know, WTF's galore but that's how it is). The application itself will effectively be an Intranet app that's hosted externally from a client but restricted by IP range along with standard username/password security. So it's pretty much a hybrid Internet/Intranet application but we can easily roll out packages of files to client machines. I am not suggesting that we expect nor require public clients to download packages of files. We have control to an extent over the client machines in terms of the local filesystem and so on but we cannot change the caching policy.
We're using UpdatePanel controls to perform partial page updates which obviously means that we need to Microsoft AJAX JavaScript files. Presently these are being served (as standard) by a standard resource handler within IIS/ASP.NET. Ideally I would like to be able to take these JS files and reference them statically from a client machine, and no longer serve them via an AXD.
My questions are:Is this possible?If it is possible, how do we go about doing so?
In order to attempt to pre-empt some WTF's the requirement stems from attempting to service a requirement with as little time and effort as possible whilst a more suitable solution is developed. I'm aware that we can lighten the load, we can switch to jQuery AJAX updates, we can rewrite the front-end in MVC etc. but my question is related to what we can quickly deploy with our existing application architecture.
Many thanks in advance :)
Lorna,
maybe your security team is going crazy. What is the difference between serving a dynamic HTML generated by the server and a dynamic JS generated by the server?
It does not make any sense. You should try talking them out of it.
what is the average size of pages and viewstate data. you might need to store viewstate in sqlserver rather than sending it to client browser every time.
I have recently started using a shared-host for my clients so see project progress or to play with a new technology for myself. I seems like every time I deploy a new project that runs fine locally, I run into something new on the shared-host.
Do you have a shared hosting deployment checklist?
What are the common problems you run into when deploying to a shared host?
Medium Trust. If you are developing code to go into a shared host, you should set your local application to run in medium trust otherwise you can almost guarantee you'll get security issues with code that executes fine in full trust but dies in a medium trust environment.
This MSDN article explains about medium trust in more detail:
http://msdn.microsoft.com/en-us/library/ms998341.aspx
They don't always offer you direct access to the database (Enterprise Manager / Management Studio).
You end up using some weird web GUI for creating database entities, which does not accept otherwise valid SQL syntax and you have to update all your queries and stored procedures to accommodate their custom changes and restrictions.
One of mine is file IO permission problems. An example being writing to a file on the web server from ASP.NET. You have to use a provided online tool to allow permission to do more than reads.
No preview site.
That is, a host based path to your web application without actually pointing the DNS to it.
Example:
http://www234.your-shared-host.com/preview/user/bla/default.aspx (don't try it, it's just an example..)
Inconvenient cancellation procedure
In some of the shared hosts I used, I found out that for cancellation I must make a phone call. Nothing over the web, not even an email.
I bet the host thinks most people won't bother calling until it's really needed. They're right.